Lifetime Nutritional Influences on Cognition, Behaviour and Psychiatric Illness

D Benton

• Publisher: Woodhead Publishing
• Year: 2011
• Print ISBN: 9781845697525
• eBook ISBN: 9780857092922
• Topic: Medicine
• Subtopic: Neurology

The influence of nutrition on cognition and behaviour is a topic of increasing interest. Emerging evidence indicates that nutrition in early life can influence later mental performance and that diet in later life can reduce cognitive decline. Lifetime nutritional influences on cognition, behaviour and psychiatric illness reviews the latest research into the effects of nutrition on cognition and behaviour across the lifespan and on psychiatric illness.Part one investigates nutritional influences on brain development and cognition including the effects of early diet and the impact of key dietary consistuents including long-chain polyunsaturated fatty acids and iron. Part two explores the link between diet, mood and cognition discussing carbohydrate consumption, mood and anti-social behaviour, hydration and mental performance and the neurocognitive effects of herbal extracts, among other topics. Part three examines nutritional influences on behavioural problems, psychiatric illness and cognitive decline, including the role of nutrition in attention deficit hyperactivity disorder, vitamin status and psychiatric disorders, antioxidants and dementia, and depression, suicide and fatty acids.With its distinguished editor and international team of expert contributors, Lifetime nutritional influences on cognition, behaviour and psychiatric illness is a valuable reference tool for researchers working on the effects of diet on the brain in both academia and industry and may also appeal to dieticians and nutritionists.- Reviews the latest research into the effects of nutrition on cognition and behaviour across the lifespan and on psychiatric illness- Explores the link between diet, mood and cognition discussing carbohydrate consumption, mood and anti-social behaviour- Examines nutritional influences on behavioural problems, psychiatric illness and cognitive decline

Part I

Nutritional infl uences on brain development

1

The effects of early diet on cognition and the brain

E.B. Isaacs and A. Lucas, UCL Institute of Child Health, UK

Abstract:

Animal studies have found effects of early nutrition on both cognition and brain structure. In humans, effects on cognition have been found in observational studies and, more recently, in randomised controlled trials but it was not possible to examine dietary effects on brain structure until the recent advent of neuroimaging. This chapter uses one particular cohort to illustrate both cognitive and brain structure findings and discusses issues arising from these studies as well as more general ones relevant to this emerging field of research.

Key words

early infant diet

nutrition and cognition

nutrition and brain structure

1.1 Introduction

Differences in specific nutrients in the diets of infants and children have been shown to have an effect on their cognitive behaviour. Studies have also shown show that diets differing mainly in their total energy/ protein content may affect subsequent cognition (Lucas et al., 1998; Grantham-McGregor and Baker-Henningham, 2005). Although neuro-scientists have largely ignored nutrition as an independent variable of interest in cognitive development, the finding should come as no surprise in view of the large animal literature that clearly illustrates the link. Smart (1986), for example, undertook a review of the animal literature to address the question of whether early under-nutrition had effects on later intellectual functioning. One hundred and sixty-five studies in non-human species (85 % in rodents) in which there had been a period of protein-energy malnutrition sometime between conception and early post-weaning, followed by at least one month of good quality diet, were reviewed. Learning and memory measures obtained from maze-running tasks were compared between previously undernourished animals and well-nourished controls. Smart concluded that the finding of significantly superior performance by the control groups predominated strongly. These studies, both in animals and humans, illustrate the role that nutrition can play in later cognitive behaviour.

Since cognitive behaviour has its basis in the brain, these findings raise the hypothesis that nutrition exerts its effects on cognition by affecting the brain, either in terms of how it is structured (anatomy) or how it functions (physiology) or both. Animal studies have been able to demonstrate this using histological methods (Dauncey and Bicknell, 1999). Studies in humans, although biologically plausible, are limited in scope and number because such methods can only be used post mortem. The few post mortem studies carried out in human infants in relation to nutrition have been informative. Benitez-Bribiesca et al. (1999), for example, reported that the brains of infants severely malnourished in early postnatal life showed pathology related to the spines of dendrites in neurons, important in nerve transmission, and maybe related to future neuropsychological deficits. This accords with the fact that dendritic spines are known to be highly responsive to changes in the environment. The use of electroencephalographic (EEG) methods to study patterns of neural electrical activity has provided some information about brain function in vivo. Hayakawa et al. (2003) compared extremely low birth weight infants in whom enteral feeding was established by three weeks after birth to those in whom it was not, finding a higher incidence of dysmature patterns of background EEG in the group with poor nutrition. Khedr et al. (2004) used evoked potentials, another EEG method, to demonstrate greater maturity of electrophysio-logical function in infants aged approximately one year who had been breastfed compared to those formula-fed. A large leap forward in our ability to study the important question of whether nutrition can affect the human brain in vivo came about with the advent of neuroimaging (Dauncey, 2009). Although still few in number, studies using this methodology to examine nutrition-brain relationships are now beginning to appear in the literature. The main concern of this chapter is to describe the methods that have become available and the results of some of the first studies to use these in the field of nutrition. To do this, we concentrate on a cohort from a particular randomised controlled trial of early infant feeding that has been studied over time using both psychological assessment and, recently, neuroimaging. After describing the cohort and the design of the randomised controlled trial, we present the cognitive results obtained at different ages and then the results of some of the first studies of the effects of nutrition on the human brain using neuroimaging methods. The issues raised by these studies are discussed along with the implications they have for future research.

1.2 Nutrition, cognition and the brain: background considerations

1.2.1 Is it biologically plausible that nutrition affects cognition and the brain?

From the time of conception, the brain of any organism is subject, first in utero and then after birth, to a large number of environmental influences, one of which is nutrition. Walker (2005) states that nutrition is the environmental variable with the greatest potential for affecting brain development. According to Wachs (2000), there is consistent evidence that the level and quality of dietary intake can affect the development of both the macrostructure and microstructure of the central nervous system (CNS) as well as the level and operation of neurotransmitters. He provides a useful summary of the evidence linking nutritional deficits to the development of behaviour. There are good reasons to expect that differences in nutritional intake might also exert influences on the everyday running of the brain. It is dietary sources, for example, that provide the metabolic resources that are necessary for the maintenance of activity in the CNS. Greenwood and Craig (1987) describe three ways in which food intake can affect neuro-chemistry: 1. by providing nutrient precursors for neurotransmitter synthesis, 2. by providing vitamins and minerals that are essential cofactors for enzymatic activity in such synthesis, and 3. by the action of some dietary fats in altering nerve cell membrane properties with an impact on neural function.

Since the underpinning of cognitive activity is brain processing, nutritional effects on the brain have the potential to affect cognitive performance. Such effects, however, will not be seen if the neural areas affected are not implicated in the cognitive activity being assessed or if the effects are too subtle to be detected by the particular tests being used. It is often assumed that groups that have the same overall cognitive level, as indexed by IQ scores, will show no differences in more specific cognitive functions, but this is not the case and differences may be missed simply because the specific functions are not assessed. It may also be that nutritional effects on the brain exist but that they cannot be detected by our present imaging techniques.

1.2.2 When might nutrition exert influence?

Nutrition, in its effects on the maintenance of normal function of the brain, has an influence across the entire lifespan. Some effects are short-term with dietary intake leading to fluctuations in the ongoing function of the brain. The intake of glucose, for example, can affect learning and memory function, particularly in the normal elderly (Gold, 1995). Convit et al. (2003) showed that reduced glucose tolerance in a group of normal adults with a mean age of 68 years was associated with degree of hippocampal atrophy. Corresponding changes in brain structure accompanying these minute-to-minute changes would not be expected.

Long-term effects on structure are more likely to happen at specific times in development. One important period is prenatally when the foetus is dependent on the maternal diet for its nutrient intake and might, in theory, be affected for the duration of pregnancy, although the third trimester seems to be the most important in terms of birth weight (Stein et al., 2004). The second is the period of greatest brain development, often referred to as the 'brain growth spurt' that occurs between the start of the third trimester of pregnancy and approximately 18 months of age in humans (Dobbing and Sands, 1973). The CNS appears to be most vulnerable to outside influences when it is developing rapidly, as is particularly true during this period, making diet in the early postnatal years of particular interest. Animal studies show that early malnutrition may have profound effects on various aspects of brain development (Rice and Barone, 2000) and human work has also tended to focus on ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Food Science, Technology and Nutrition
• Introduction
• Part I: Nutritional infl uences on brain development
• Part II: Diet, mood and cognition
• III: Nutritional infl uences on behavioural problems, psychiatric illness and cognitive decline associated with ageing
• Index